-
Notifications
You must be signed in to change notification settings - Fork 2
/
Copy pathmpm128_ggui_jelly_only.py
196 lines (169 loc) · 6.8 KB
/
mpm128_ggui_jelly_only.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
import numpy as np
import taichi as ti
ti.init(arch=ti.gpu) # Try to run on GPU
quality = 1 # Use a larger value for higher-res simulations
n_particles = 3000 * quality ** 2
n_grid = 128 * quality
dx = 1 / n_grid
inv_dx = float(n_grid)
dt = 1e-4 / quality
p_vol = (dx * 0.5) ** 2
p_rho = 1
p_mass = p_vol * p_rho
E = 5e3 # Young's modulus
nu = 0.2 # Poisson's ratio
mu_0 = E / (2 * (1 + nu))
lambda_0 = E * nu / ((1 + nu) * (1 - 2 * nu)) # Lame parameters
x = ti.Vector.field(2, dtype=float, shape=n_particles) # position
v = ti.Vector.field(2, dtype=float, shape=n_particles) # velocity
C = ti.Matrix.field(2, 2, dtype=float, shape=n_particles) # affine velocity field
F = ti.Matrix.field(2, 2, dtype=float, shape=n_particles) # deformation gradient
material = ti.field(dtype=int, shape=n_particles) # material id
Jp = ti.field(dtype=float, shape=n_particles) # plastic deformation
grid_v = ti.Vector.field(
2, dtype=float, shape=(n_grid, n_grid)
) # grid node momentum/velocity
grid_m = ti.field(dtype=float, shape=(n_grid, n_grid)) # grid node mass
gravity = ti.Vector.field(2, dtype=float, shape=())
gravity[None] = [0, -1]
attractor_strength = ti.field(dtype=float, shape=())
attractor_pos = ti.Vector.field(2, dtype=float, shape=())
# group_size = n_particles // 3
group_size = n_particles
# water = ti.Vector.field(2, dtype=float, shape=group_size) # position
jelly = ti.Vector.field(2, dtype=float, shape=group_size) # position
# snow = ti.Vector.field(2, dtype=float, shape=group_size) # position
mouse_circle = ti.Vector.field(2, dtype=float, shape=(1,))
max_nodal_mass = ti.field(dtype=float, shape=())
@ti.kernel
def substep():
# clear grid
for i, j in grid_m:
grid_v[i, j] = [0, 0]
grid_m[i, j] = 0
# Particle state update and scatter to grid (P2G)
for p in x:
base = (x[p] * inv_dx - 0.5).cast(int)
fx = x[p] * inv_dx - base.cast(float)
# Quadratic kernels [http://mpm.graphics Eqn. 123, with x=fx, fx-1,fx-2]
w = [0.5 * (1.5 - fx) ** 2, 0.75 - (fx - 1) ** 2, 0.5 * (fx - 0.5) ** 2]
F[p] = (ti.Matrix.identity(float, 2) + dt * C[p]) @ F[
p
] # deformation gradient update
h = 1
mu, la = mu_0 * h, lambda_0 * h
U, sig, V = ti.svd(F[p])
J = 1.0
for d in ti.static(range(2)):
new_sig = sig[d, d]
Jp[p] *= sig[d, d] / new_sig
sig[d, d] = new_sig
J *= new_sig
stress = 2 * mu * (F[p] - U @ V.transpose()) @ F[
p
].transpose() + ti.Matrix.identity(float, 2) * la * J * (J - 1)
stress = (-dt * p_vol * 4 * inv_dx * inv_dx) * stress
affine = stress + p_mass * C[p]
for i, j in ti.static(ti.ndrange(3, 3)): # Loop over 3x3 grid node neighborhood
offset = ti.Vector([i, j])
dpos = (offset.cast(float) - fx) * dx
weight = w[i][0] * w[j][1]
grid_v[base + offset] += weight * (p_mass * v[p] + affine @ dpos)
grid_m[base + offset] += weight * p_mass
for i, j in grid_m:
ti.atomic_max(max_nodal_mass[None], grid_m[i, j])
# update grid
for i, j in grid_m:
if grid_m[i, j] > 0: # No need for epsilon here
grid_v[i, j] = (1 / grid_m[i, j]) * grid_v[i, j] # Momentum to velocity
grid_v[i, j] += dt * gravity[None] * 30 # gravity
dist = attractor_pos[None] - dx * ti.Vector([i, j])
grid_v[i, j] += (
dist / (0.01 + dist.norm()) * attractor_strength[None] * dt * 100
)
if i < 3 and grid_v[i, j][0] < 0:
grid_v[i, j][0] = 0 # Boundary conditions
if i > n_grid - 3 and grid_v[i, j][0] > 0:
grid_v[i, j][0] = 0
if j < 3 and grid_v[i, j][1] < 0:
grid_v[i, j][1] = 0
if j > n_grid - 3 and grid_v[i, j][1] > 0:
grid_v[i, j][1] = 0
# grid to particle (G2P)
for p in x:
base = (x[p] * inv_dx - 0.5).cast(int)
fx = x[p] * inv_dx - base.cast(float)
w = [0.5 * (1.5 - fx) ** 2, 0.75 - (fx - 1.0) ** 2, 0.5 * (fx - 0.5) ** 2]
new_v = ti.Vector.zero(float, 2)
new_C = ti.Matrix.zero(float, 2, 2)
for i, j in ti.static(ti.ndrange(3, 3)): # loop over 3x3 grid node neighborhood
dpos = ti.Vector([i, j]).cast(float) - fx
g_v = grid_v[base + ti.Vector([i, j])]
weight = w[i][0] * w[j][1]
new_v += weight * g_v
new_C += 4 * inv_dx * weight * g_v.outer_product(dpos)
v[p], C[p] = new_v, new_C
x[p] += dt * v[p] # advection
@ti.kernel
def reset():
for i in range(n_particles):
x[i] = [
ti.random() * 0.2 + 0.3 + 0.10 * (i // group_size),
ti.random() * 0.2 + 0.5 + 0.32 * (i // group_size),
]
# material[i] = i // group_size # 0: fluid, 1: jelly, 2: snow
material[i] = 1 # 0: fluid, 1: jelly, 2: snow
v[i] = [0, 0]
F[i] = ti.Matrix([[1, 0], [0, 1]])
Jp[i] = 1
C[i] = ti.Matrix.zero(float, 2, 2)
@ti.kernel
def render():
for i in range(group_size):
jelly[i] = x[i]
# water[i] = x[i]
# jelly[i] = x[i + group_size]
# snow[i] = x[i + 2 * group_size]
print(
"[Hint] Use WSAD/arrow keys to control gravity. Use left/right mouse bottons to attract/repel. Press R to reset."
)
res = (512, 512)
window = ti.ui.Window("Taichi MLS-MPM-128", res=res, vsync=True)
canvas = window.get_canvas()
radius = 0.003
reset()
gravity[None] = [0, -1]
while window.running:
if window.get_event(ti.ui.PRESS):
if window.event.key == "r":
reset()
elif window.event.key in [ti.ui.ESCAPE]:
break
# if window.event is not None:
# gravity[None] = [0, 0] # if had any event
# if window.is_pressed(ti.ui.LEFT, "a"):
# gravity[None][0] = -1
# if window.is_pressed(ti.ui.RIGHT, "d"):
# gravity[None][0] = 1
# if window.is_pressed(ti.ui.UP, "w"):
# gravity[None][1] = 1
# if window.is_pressed(ti.ui.DOWN, "s"):
# gravity[None][1] = -1
mouse = window.get_cursor_pos()
mouse_circle[0] = ti.Vector([mouse[0], mouse[1]])
canvas.circles(mouse_circle, color=(0.2, 0.4, 0.6), radius=0.05)
attractor_pos[None] = [mouse[0], mouse[1]]
attractor_strength[None] = 0
if window.is_pressed(ti.ui.LMB):
attractor_strength[None] = 1
if window.is_pressed(ti.ui.RMB):
attractor_strength[None] = -1
for s in range(int(2e-3 // dt)):
substep()
render()
canvas.set_background_color((0.067, 0.184, 0.255))
# canvas.circles(water, radius=radius, color=(0, 0.5, 0.5))
canvas.circles(jelly, radius=radius, color=(0.93, 0.33, 0.23))
# canvas.circles(snow, radius=radius, color=(1, 1, 1))
window.show()
print(max_nodal_mass[None])